1. Technical Field
The present invention relates to a liquid ejecting apparatus provided with a plurality of heads for ejecting a liquid, and, in particular, to a technique for circulating a liquid through a plurality of heads.
2. Related Art
One known example of this type of liquid ejecting apparatus is an inkjet recording apparatus disclosed in Japanese laid-open patent publication 2011-79169. With this apparatus, ink supplied from an ink tank is distributed with an ink supply manifold. More specifically, the ink is distributed and supplied to respective head modules via a first branching flow path extending from the ink supply manifold. In turn, ink that is discharged from each of the head modules is recovered in an ink recovery manifold via a second branching flow path, and moreover is returned to the ink tank from the ink recovery manifold. This constitutes an ink circulation system with which ink is supplied from an ink tank and passes through a plurality of heads, and the ink is again recovered in the ink tank.
In the apparatus disclosed in Japanese laid-open patent publication 2011-79169, both the ink supply manifold and the ink recovery manifold have provided therein an internal flow path sufficiently thick enough for gas and the ink to separate up and down when there is admixed gas in the ink. Here, provided that the cross-sectional areas of the internal flow paths are constant, then the pressure loss varies every instance of passage through the branching flow paths. In particular, the recovery side (also called the return side) is majorly impacted by the pressure fluctuations, and this leads to a decrease in the ejection performance of the liquid. That is to say, both of the internal flow paths have a constant flow path resistance in a case where the internal flow path of the ink recovery manifold has a constant cross-sectional area. Therefore, at every instance of passage through the second branching flow path, the flow rate inside the internal flow path increases and the pressure loss grows. As a result, the pressure on the meniscus of the nozzles of each of the heads varies greatly and every head ends up having a different ejection of liquid.